Geographical isolation

Spatial or geographical isolation is the kind of isolation that prevents interbreeding between populations allopatric because it occurs in separate, nonoverlapping geographic areas. Often used of populations of related organisms unable to crossbreed because of geographic separation. If this isolation persists for a long time could lead people to differentiate morphologically in response to check for different environments. If the geographic barrier disappeared two situations may happen:
a) populations may return to interbreeding thus forming a single population;
b) whether the geographical isolation continues for a sufficiently long period, populations may differentiate such that the interbreeding between them is no longer possible, thus appearing reproductive isolation.

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